Metallurgy of lead, tin, and other metals



Dec. 2, 1941.

W. SEGUINE ETAL METALLURGY OF LEAD, TIN, AND OTHER METALS Filed Aug. 2,1940 METALLURGICAL FUMES I M IX WITH WA'fiER COARSE PARTICLES ATTACKWITH H, S 0 IN DISSQLVING TAN K SEPARATION OF RESIDUE AND WASHING- HIGHZINC Pb-$n RESIDUE I CNLORIOES VOL-AT'ILIZEP AND RETURN WASH ua R086M111: MATTER cousuMED LIQU R Cu C MPOUNDS Pb C MPOUNDS XYGEN WITH A5M086 l DRYER M X WIT]; CARBaN AND AGGLOMERAMS Inning) SMELT IN FURNA (EAND REMQIYE SLAG INTER UNDER INDUCED DRAFT I I 50 1 MIX WIT/l COKE ANDFLX may; OFF

Pb-Sn ALLOY CONTAIN/N6 AS,SbAIvn urns 0F Cu l DIOSSING' KETTLE A B0 SAWDUS 7' was? bless AT sscouo DROSS A1 men TEMPERATURE LOW TEMPERATURE I5man m cu ls" Low m cu Law In As HIGH In As LOW IN Sn SUBSTANTIA Sn CONTENT PURIFIED WILLIAM sseum:

FRANK HILLIS abtowog Patented Dec. 2 1941 METALLURGY F LEAD, TIN, ANDOTHER I METALS William Seguine and Frank N. Hillis, Baltimore,

Md., assiguors to The Glidden Company, Cleveland, Ohio, a corporation ofOhio Application August 2, 1940, Serial No. 350,089

14 Claims.

This invention relates to the metallurgy of lead and tin and especiallyto the smeltingof certain lead-tin residues existing as lead sulfate andtin oxide and contaminated by small quantities of copper, arsenic andantimony.

Among the objects of this invention is the economical recovery of alead-tin alloy suitable for the commercial production of solder, typemetal and analogou alloys.

A further object of this invention is the economical recovery oflead-tin alloys from low grade residues.

A further object of this invention is the purification of lead-tinalloys from impurities, such as copper and zinc. Y

A further object of this invention is the economic desulfurization ofmetalliferous material comprising mainly PbSOy'and SnOz, and includingsubstantial content of powdery material. This invention also comprisesthe desulfurization of metalliferous material comprising PbSO4, SnO-z,copper compounds and oxygenated lead compounds of arsenic and antimonyand including substantial content of powdery material. A still furtherobject of this invention is "the removal of impurities, such as copperand arsenic, from metalliferous material comprising 'mainlyPbSOa andS110: and including substantial content of powdery material.

Other, further and more specific objects of and such compounds at a hightemperature volatilize on account of their respective high vaporpressures.

Further, on account of these residues, substantial mechanical lossesoccur in smelting. Accordingly, we have found it economical andexpedient to subject these residues to a preliminary treatment prior tosmelting and this preliminary treatment, which involves the fineparticle size of 5 lead sulfide and tin sulfide are or may be formed,

desulfurization and agglomeration, is best accom plished by'means of antermed sintering.

operation technically mixed with approximately 7 to 9% carbon, usuallyin the form of coke or coal, together with about 10 to 12% water. Thiswater has the effect of pelleting or balling up the fine residues tosuch a form that a charge thereof is readily permeable to a blast ofair. The charge so prepared is placed upon the grates of a sinteringapparatus of the downdraft type, such' as exemplified by the well knownDwight Lloyd apparatus, although we do not limit ourselves to thismachine in 'the practice of our invention. t} I Combustion of the carbonby igmtlon and induced draft has the effect of bringing the charge to avery high heat so that the lead sulfate con-.

tent is substantially reduced to lead oxide. This lead oxide, which isreadily fusible and which readily combines in part with the tin oxidecontent, forms thereby a sintered or agglomerated tin residue are almostquantitatively reduced with the lead and tin, so that the metal alloyoflead and tin contains very substantial amounts of copper, antimony andarsenic. It is necessary, therefore, to remove these impurities bydressing.

The economical separation resulting in recovery of valuable metals inthis dross is an important feature of our invention. For example,whenproducing by this process a characteristic leadtin alloy assaying25% tin it wfll usually contain about 1.5% antimony and about 2%arsenic. Also, it will contain varying amount of copper; that is, from 2to 3%, if the aforesaid lead-tin residue is produced from ordinary zincfume derived from the smelting of copper ores.

If a lead-tin alloy, such as described, is m d in an appropriate vesselor kettle, and th perature raised to. about 800 F. and then slowlycooled, it will be found that a dross appears upon the surface of themetal. If the contents of the kettle. be agitated by a suitable stirrer,the production of this dross will be expedited. However, this dross willcontain substantial quantities of entrained alloy. Sawdust is added andstirred into the metal, which operation has the eflect of what is knowntechnically .as drying" of the dross. This drying efiect is most likelydue'to the fact that the sawdust on charring decreases reduced to.8%-l%.

the ability of the molten alloy to wet the dross. Other drying agentsmay be used.

We have found that this drossing continues down almost to the meltingpoint of the alloy and, if continued carefully, the copper content andarsenic contentcan be reduced to less than 0.2%. The antimony content,however, does not decrease so. much, although we have found thatimportant quantities will pass into the dross.

We have discovered that thedross formed with the progressive cooling ofthe metal varies very substantially in its copper and arsenic content.We have found that copper passes to the-dross in the higher reaches ofthe cooling curve and that arsenic passes into the dross moresubstantilelly as we approach the melting point of the a oy.

Furthermore, we have found that the tin content of the dross rises asthe temperature at which the drossing is conducted falls. As a result ofthese discoveries, we, have found it possible to segregate the drossesinto portions and prefer in general, for purposes of convenience inmanufacture, to produce onlyfitwo fractions, one of which is ahigh-copper, low-arsenic dross containing comparatively little tin andsecond a low-copper, high-arsenic dross with a very substantial tincontent. 7

This segregation of the respective drosses enables us to economicallyrecover the metal content; To effectuate this, we return the highcopper'dross to the roasting furnace where the metallurgical zinc fumes arefirst treated This dross, when mixed with the original zinc fume, isroasted readily, to such a form that the copper content becomesacid-soluble and is recovered substantially as herein later described.The tin contents of the dross at the same time also rejoi n the tincontent in the metallurgical fumes.

The high-arsenic, high-tin dross is returned to the aforesaid sinteringmachine We have found that the arsenic content substantially volatilizesand can be thereby removed from the smelting circuit.

It must be noted that the arsenic content of the original lead-tin fumeis present as ar'seniates of lead, in which form arsenic is not readilyrequires considerable energy for its decomposition. However, the arsenicpresentin the dross exists as arsenide, in which form the arsenic firstsmelting these ores, concentrates, etc., with coke and fluxes inappropriate blast furnaces, forming thereby a compound composed ofcopper, iron and sulfur which is termed a matte. This matte, while stillin a liquid condition, is further treated by the well known Bessemerprocess whereby the iron and sulfur are removed and finally blistercopper is obtained. The blister copper is further refined to purecommercial copper, by electrolytic treatment.

Since, in the vicinity of some copper smelters there is available a verylarge quantity of scrap copper materials, it is customary to treat thesescrap materials together with the aforesaid ores and concentrates.Non-metallic scrap, for example, oxidized materials, is customarilycharged into the blast furnace, whereas coarse m'etailics may be placedin the Bessemer converter and so treated. This scrap, however, willalmost invariably contain large amounts of zinc, lead and tin, so thatin copper smelting it is found that these metals, on account of theirvolatility and the volatility of their compounds, are fumed out into theblast furnace gasesand also into the converter gases. To avoid publicnuisance and for economic reasons, it is necessary to cool and filterthese gases through appropriate devices, such as woolen bags, electricalprecipitators, and the like, so that the smelter may discharge aharmless gas to the atmosphere.

By this means, a fume is collected which will analyze approximately asfollows:

Per cent Zinc Lead 15 Tin 4 Copper 1 Iron 0.5 Arsenic 0.3 Antimony 0.3Chlorine 1.5

In addition, there will be present various indeterminable quantities oforganic matter derived from the coke-and organic constituents of thesmelter charges. I V This zinc content exists substant1ally as zinc.oxide, with minor amounts of zinc sulfate and volatilized in thesintering machine since it readily passes into a gas. It is, therefore,clear 3 that by the segregation of these drosses-we have provided meansfor satisfactorily removing an economic manner the copper and thearsenic from .the tin-lead alloy.

Also, the removal of antimony is not as simple zinc chloride, and isreadily extractable from the.

fume by sulfuric acid. However, when this fume is leached with sulfuricacid, the resulting zinc sulfate is quiteimpure, containing as it doessubstantial amounts of zinc chloride and organic matter.

Reference may be had to the accompanying drawing, which shows a flowsheet,

Aspecific example of carrying out our invention is as follows:

as the removal of arsenic although we very simply. reduce the arseniccontent of such metal from say 2% to 25%. The antimony, which may-be1.5% in the crude alloy, can only be However, from the commercialstandpoint this is not of importance,

because it has been found that about 1% anti mony in these alloys ispermissible.

The specific m'etalliferous material comprising PbSOa, SnOz, coppercompounds and oxygenated lead compounds of arsenic and antimony, for thetreatment of which our invention is particularly adapted, is obtainedfrom byproduct, zinc fume pr uced during the smelting of secondarynonerrous metals. 1

In the smelting of copper, it is usual to recover copper from ores,concentrates and the like by A metallurgical fume asheretofore-described and of the aboveanalysis is mixed with 15-25% waterand agglomerated into coarse granules, balls and pellets and thenroasted at 600-800 C.

The organic matter of the fume is consumed and (I the chloride contentis substantially all driven off byvolatilization.

The roasted product is then attacked with H2804 in a dissolving tank andthe residue or' pulp is separated from the liquor by sedimentation,filtration and/or centrifugal action. The residue is then; washed and weprefer to return the wash water to the dissolving tank, where theroasted mass is attacked with H2304. The liquor, which is separated fromthe pulp after the acid treatment,ris practically free-of chlorides andconsists chiefly of ZnSOrsolution and also small quantities of thesulfates of Cu, Fe, Cd and Ni. Manganese sulfate is also sometimes foundin small quantities. This liquor is now subjected to the usualpurification andrefini ng, whereby pure ZnSO4 solution is obtained. Fromthis pure ZnSO4 solution pure metallic zine, ZnS and/or lithopone may beobtained, of high grade andquality.

The washed residue, consisting chiefly of PbSO4 and $1102 with a smallcontent of copper compounds and oxygenated lead compounds'of arsenic andantimony, is dried and then mixed with approximately 7-9% carbon (in theform of coal or coke) together with about 10-12% of water. This wettedmaterial is then agglomerated into coarse granules, balls and pellets,

after which it is placed upon the grates of a sintering apparatus of thedowndraft type; such as exemplified by the well known Dwight Lloydapparatus. During this sintering, the lead sulfate content issubstantially reduced to lead oxide. This lead oxide, which exists incombination with tin as a sinter, is then mixed with lump coke and asuitable flux and then charged into the prefer to return this fractionto the roaster where it is mixed and treated with the granules. ballsand pellets of the metallurgical'fume, to which water has been added.

The second fraction. obtained in the lower reaches of the cooling curve,is a low-copper,

high-arsenic dross with a very substantial tin.

content. We prefer to return this fraction to the sintering machine,where it is mixed and treated with the coarse particles, balls andpellets of the residue to which coke has been added. During thistreatment, the arsenic content of the dross substantially volatilizesand can be thereby removed from the smelting circuit.

After the fractional dressing, the remaining metal is removed from thedrossing kettle and this is a high-grade, purified lead-tin alloy.

The present invention is not limited to the specific details set forthinthe foregoing examples which sho ld be construed as illustrative andnot by way of itation, and in .view of .the numerous modifications whichmay be effected therein without departing from the spirit and scope ofthis invention, it is desired that only such limitations be imposed asare indicated in the appended claims. r

We claim as our invention:

1. In a process of smelting metalliferous material comprising PbS04,SnOz, coppercompounds and oxygenated lead compounds of arsenic andantimony and including a substantial powdery content. mixing saidmetalliferous material with carbon and water and forming coarseparticles thereof, then subjecting the mass of coarse material tosintering under induced draft. whereby S0: is driven off, the PbSOq isreduced to PM and the metalliferous charge isdesulfurized and sintered,mixing the resulting desulfurized sinter with carbon and a flux andsmelting same whereby alloy and slag are formed, then removing drosscontaining copper, arsenicand tin from the molten alloy and thenvolatilizing the arsenic connt from said dross by sintering same withcar- 2. Ina process of smelting metalliferous material comprising mainlyPbSOr and S1102 with small content of copper compounds and oxygenatedlead compounds of arsenic and antimony and' including a substantialpowdery content, mixing said metalliferous material with carbon andwater and forming coarse particles thereof, then subjecting the mass ofcoarse material,to sintering under induced draft, whereby SO2 is 'drivenoil, the PbSO4 is reduced to Rho and the metalliferous charge isdesulfurized and sintered',

mixing the resulting desulfurized sinter with car-.

bon and a flux and smelting same whereby alloy and slag are formed, thenfractionally' re-- moving dross containing copper, arsenic and tin fromthe molten alloy and then volatilizing the arsenic content-from fractionof said dross of high arsenic content by sintering said fraction withcarbon.

3. In a. process of smelting metalliferous material comprising PbSOi,SnOz, copper compounds and oxygenated lead compounds of arsenic andantimony and including a substantial powdery content, mixing saidmetalliferous material with carbon and water and forming coarseparticles thereof, then subjecting the mass of coarse material tosintering under induced draft, whereby .02 is driven on, the peso, isreduced to PbO and the metalliferous charge is desulfurized and'sintered, mixing the resulting desulfurized sinter with carbpn and aflux and smelting same whereby-alloy and slag are formed, thenfractionally removing dross containing copper, arsenic and tin from themolten alloy while the molten metal is cooled and then volatilizing thearsenic content from fraction of said dross ofhigh arsenic content bysintering said fraction with carbon.

4. In a process of smelting metalliferous material comprising mainlyPbSO4 and $1102 with small content of copper compounds and oxygenatedlead compounds of arsenic and antimony and including a substantialpowdery content, mixingsaid metalliferous material with carbon and waterand forming coarse particles thereoiigthen subjecting the mass of coarsematerial to sintering' under induced draft, whereby S0: is driven off,the PbSO4 is reduced to PbO and the metalliferous charge is desulfurizedand sintered, mixing the resulting desulfurized sinter with carbon and aflux and smelting same whereby alloy and ,.slag2are ..forfiied, and thenfractionally removing dross containing copper, arsenic and tin from thesurface of the molten alloy while the molten metal is slowly cooled.

5. In a process of smelting metalliferous material comprising PbSO4,SnOz, copper compounds and oxygenated lead compounds of arsenic andantimony and including a substantial powdery content, mixing saidmetalliferous material-with carbon and water and forming coarseparticles thereof, then subjecting the mass of coarse material tosintering under induced draft. whereby $05 is driven 01!, the PbSOiisreduced to PhD and the metalliferous charge is desulfurized andsintered, mixing the resulting desulfurized sinter with carbon and aflux and smelting same whereby alloy and slag are formed, adding adrying agent to the molten mass and fractionally removing drosscontaining copper, arsenic and tin from the molten alloy while themolten metal is cooled.

6. In a process of smelting metalliferous material comprising PbSO4,S1102, copper compounds and oxygenated lead compounds of arsenic andantimony and including a substantial powdery content, mixing saidmetalliferous material with carbon and water and forming coarseparticles thereof, then subjecting the mass of coarse material tosintering under induced draft, whereby S02 is driven off, the PbSO4 isreduced to PbO and the metalliferous charge is desulfurized andsintered, mixing the resulting, desulfurized sinter with carbon and aflux and smelting same whereby alloy and slag are formed, adding sawdustto the molten mass and fractionally removing dross containing copper,arsenic and tin from the surface of the molten alloy while the moltenmetal is slowly cooled.

7. In a process of smelting metalliferous material comprising PbSO4,SnO'z, copper com pounds and oxygenated lead compounds of arsenic andantimony and including a substantial powdery content, mixingsaidmetalliferous material withcarbon and water and forming coarseparticles thereof, then subjecting the mass of coarse material tosintering under induced draft, whereby S02 is driven off, the PbSO4 isreduced to PbO and the metalliferous charge is desulfurized andsintered, mixing the resulting desulfurized sinter with carbon and aflux and smelting same whereby alloy and slag are formed, and thenremoving dross containing copper, arsenic and tin from the molten alloy,a fraction of the dross high in copper and low in arsenic and tin beingremoved at a higher temperature and a fraction of the dross low incopper and high in arsenic and tin being removed at a lower temperature.

8. In a process of smelting metalliferous material comprising mainlyPbSO4 and SnO: with small content of copper compounds and oxygenatedlead compounds of arsenic and antimony and including a substantialpowdery content, mixing said metalliferous material with carbon andwater and forming coarse particles thereof, then subjecting the mass ofcoarse material to sintering under induced draft, whereby S02 is drivenoff, the PbSO4 is reduced to PhD and the metalliferous charge isdesulfurized and sintered, mix ing the resulting desulfurized' sinterwith carbon and a flux and smelting same whereby alloy and slag areformed, then fractionally removing dross containing copper, arsenic andtin from the molten alloy, while the molten mass is cooled. a fractionof the dross high in copper and low in arsenic and tin being removed ata higher temperature and a fraction of the dross low in copper andhigh'in arsenic and tin being removed at a lower temperature, and thensintering the latter fraction with carbon, whereby the arsenic ,contentis volatilized from said latter fraction.

9. In a process of treating powdery material containing organic matterand zinc, lead, tin, cadmium, nickel, copper, iron, arsenic, antimonyand chlorine compounds, said process comprising adding water to saidpowdery material and forming coarseparticles thereof, then roasting saidcoarse particles, extracting the roasted product with acid,,mixing theresidue after said acid extraction with carbon and water and formingcoarse particles thereof, then subjecting the mass of coarse material tosintering under induced draft, whereby S02 is driven off, the PbSO4 isreduced to PhD and the metalliferous charge is desulfurized andsintered, mixing the resulting desulfurized sinter with carbon and aflux and smelting same whereby alloy and slag are formed, and thenremoving dross containing copper, arsenic and tin from the molten alloy,a fraction of the dross high in copper and low in arsenic and tin beingremoved at a higher temperature. and a fraction of the dross low incopper and high in arsenic and tin being removed at a lower temperature.

10. In a process of treating powdery material containing organic matterand zinc, lead, tin, cadmium, nickel, copper, iron, arsenic, antimonyand chlorine compounds, said process comprising adding water to saidpowdery material and forming coarse particles thereof, then roastingsaid coarse particles, extracting the roasted product with acid, mixingthe residue after said acid extraction with carbon and water and formingcoarse particles thereof, then subjecting the mass of coarse material tosintering under induced draft, whereby S02 is driven off, the PbSO4' isreduced to PhD and the metalliferous charge is desulfurized andsintered, mixing the resulting desulfurized sinter with carbon and aflux and smelting same whereby alloy and slag are formed, thenfractionally removing dross containing copper, arsenic and tin from themolten alloy, while the molten mass is cooled, a fraction of the drosshigh in copper and low in arsenic and. tin being removed at a highertemperature and added to coarse particles of said powdery material forroasting and a fraction of the dross low in copper and high in arsenicand tin being removed at a lower temperature andthen sintering thelatter fraction with carbon, whereby the arsenic content is volatilizedfrom said latter fraction.

11. In a process of treating metallurgical fume containing organicmatter and zinc, lead, tin, cadmium, nickel, copper, iron, arsenic, antony and chlorine compounds, said process comprising adding water to saidmetallurgical fume and form- 'ing coarse particles thereof, thenroasting said coarse particles, extracting the roasted product withH2804, mixing the residue after said acid extraction with carbon andwater and forming coarse particles thereof, then subjecting the mass ofcoarse material to'sintering under induced draft, whereby S02 is drivenoff, the PbSO4 is reduced to PhD and the metalliferous charge isdesulfurized and sintered, mixing the resulting desulfurized sinter withcarbon and a flux and smelting same whereby alloy and slag are formed.then fractionally removing dross containing copper, arsenic and tin fromthe molten alloy, while the molten mass is cooled, a fraction of thedross high in copper and low in arsenic and tin being removed at ahigher temperature and added to coarse particles of said metallurgicalfume and a fraction of the dross low in copper and high in arsenic andtin being removed at a lower temperature and added to said coarseparticles of carbon and residue after said acid extraction forsintering, whereby the arsenic content is volatilized from'said latterfraction. v

l2. In a process of refining arsenical and cuperiferous lead-tin alloy,fractionally removing dross containing copper, arsenic and tin from thesurface of the molten alloywhile the molten metal is slowly cooled, afraction of the dross highin copper and low in arsenic and tin beingremoved at a higher temperature and a fraction of the dross low incopper and high in arsenic and tin being removed-at a lower temp fromsaid latter fraction.

perature, and then sintering the latter fraction with carbon, wherebythe arsenic content is volatilized from said latter fraction.

13. In a process of refining arsenical and cuperiferous lead-tin alloy,adding a drying agent 14. In a process of refining arsenical andcuperiferous lead-tin alloy, adding sawdust to the molten alloy andfractionally removing dross containing copper, arsenic and tin from thesurface of the molten alloy while the molten metal is slowly cooled, afraction of the dross high incopper and low in arsenic and tin beingremoved at 'a higher temperature and a fraction of the dross low incopper and high in arsenic and tin being removed at a lower temperature,and then sintering the latter fraction with carbon, whereby the arseniccontent is volatilizedfrom said latter fraction;

WILLIAM SEGUDIE. FRANK N. HlLLIS.

